engine and drivetrain electrical issue... ignition relay?

[robsanab]

on my '75 there is a relay (round can) that is attached to the ignition plug under the dash. In other words, all the various wires from the ignition switch go to a plug, on the other side of this plug is this relay. What does it do?

I have had some odd, intermittent electrical problem... the car will be running great and then just turn off like the key is switched off... sometimes several times in a row I will try to restart it and it fires while the engine is cranking but dies as soon as I stop cranking. Once it starts and stays running I may not have the problem occur again for a day or two.

I have a 2 year old Crane XR700 ignition with their coil and I've checked many of the connections at the switch and associated coil terminations... all seems well. The ignition switch is old and worn enough that I can take the key out while it's running. I've tried to replicate the condition by jiggling the key, but the problem doesn't reoccur... so I'm thinking the switch may be OK

Any ideas? This is driving me crasy!

Thanks

Rob

[BillWilliams]

that familiar with square light cars. However, here is what I have to offer.

That round can by the switch in my 72 is a buzzer for when you leave the keys in the car. The starter relay in the round light cars is under the hood behind the coil on the bulkhead.

Your cutting out problem is hard to diagnose, I would try two things. Which one you try first is up to you. I would replace the coil. Sometimes when the coil heats ups it cuts out. If that does not work, I would try replacing the the switch.

Good luck!

[BillWilliams]

The switch has two circuits and I can not describe them in detail, but one circuit kicks the starter in as you hold it in the start mode, and as you release it to the run mode, it kicks the starter out while the other circuit keeps the car running.

It sounds like the wire that "keeps the car running" after start, is not staying engaged and/or cutting out under heat.

That is the way to hot wire a car, connect the two wires that "keep the car running" and momentarily connect the starter wire to those two wires while the car is turning over.

Maybe someone with a square light wiring diagram can chime in with the correct colored wires at the switch.